AND HERE is a new resource, which goes into even more detail. But FIRST get your shelter in place kit ready (ABOVE), you might need it in the next week if they don't fix Fukushima power supply. Much of the below resources deal with nuclear attack, but in reality a Nuclear Plant meltdown is very similar, in fact the Nuke Plant can be far worse. In the Nuke bomb, a very large perfect of the radiation is Iodine which goes away 1/2 every 8 days, if you can shelter 24 days, then 7/8's have become harmless, but there are still other isotopes with half lives of 30 years and more, Cesium and Strontium as notable mentions.